This application relates to position sensors, and more particularly, to a vehicle door position sensing system.
In order to determine the position of a vehicle door an optical position encoder is employed. An optical sensor may draw as much as 35-40 mA of current whenever a vehicle door is open so as to keep track of the door or gate position. This current consumption is undesirable as it will discharge the vehicle battery. To conserve energy, some systems shut down after the vehicle door has been opened for an extended period of time. However, once the system is shut down, the current position of the door must be determined again after the system is powered back up. Accordingly, there is a need for a position sensor for use in automotive applications whereby the electrical draw of such a sensor is limited.
A position sensing system that utilizes a sensor or sensors to provide an output corresponding to the position of an object is disclosed in this application. The sensor output is converted to logic level signals, which are inputted into a control system. The position sensing system utilizes a sensor or sensors requiring no external power and provide an output corresponding to the position of an object.
A very low power quadrature position sensing system includes a first sensor, which defines a starting point of a first channel. The first sensor is coupled to a first square wave generator. A second sensor signal is in quadrature with the first sensor. The second sensor defines a starting point of a second channel having very low energy consumption. The second sensor is coupled to a second square wave generator. In one embodiment, the system includes a fixed member having a first sensor, and a second sensor, and a moving member which moves relative to the fixed member. The moving member has a magnetized surface. The magnetized surface has a magnetic distribution disposed thereon to be sensed by both the first sensor, and the second sensor. During movement by the moving member, the first sensor generates a high signal and a low signal. The high signal forms a rising edge and the low signal forms a falling edge of a square wave generated by the first square wave generator. During movement of the moving member, the second sensor generates a high signal and a low signal. The high signal forms a rising edge and the low signal forms a falling edge of the square wave generated by the second square wave generator. An exemplary method for very low power quadrature position sensing includes a determination of a first set of sensed signals using a first sensor and a determination of a second set of sensed signals using a second sensor. A first sequence of square waves is determined from the first set of sensed signals. The method further includes a derivation of a second sequence of square waves from the second set of sensed signals that are in quadrature with the first sequence of square waves. A redundancy sequence signal is generated using a redundancy circuit that comprises a transistor, electronic switch, or equivalent thereof.